Specification of the design snow loads for gable roofs based on a consistent probabilistic approach

基于一致概率方法的山墙屋顶设计雪荷载规范

• 批准号: 99264718
• 负责人: Privatdozent Dr.-Ing. Michael Kasperski
• 金额: --
• 依托单位: Forschungsteam EKIB - Entwurfsgrundlagen im Konstruktiven Ingenieurbau
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2009
• 资助国家: 德国
• 起止时间: 2008-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/99264718?language=en
• 关键词: Specification; design; snow; loads; gable

One of the basic tasks of codification in regard to climatologic actions is the area-wide specification of the design values based on observations for single stations. The statistical stability of the estimated values greatly depends on the ensemble size. This is true for the estimates of each single station as well as for the geostatistical interpolation, i.e. the more observations are sampled for the single station ensembles and the more stations are used as input for the geostatistical interpolaten the higher is the statistical stability of the results. For 224 stations in Germany, extreme value statistics can be performed directly based on the observed water equivalents, which are available on average for 37 years. The developed probabilistically equivalent snow density model in combination with the new approach of using independent events instead of yearly extremes leads to considerable larger ensemble sizes with 130 entries on average. The translation of the single station model to regional models allows analysing a further 525 stations which provide only observations of the height of the snow cover. A further improvement, i.e. a reduction of the statistical uncertainties, is obtained by introducing super-stations which combine observations from single stations following a consistent probabilistic strategy. Then, the type of distribution can be identified with a sufficient statistical stability. Aim of the project is the utilization of the observed snow height data in the scope of the extreme value statistics of the snow loads and the statistical optimal specification of the corresponding design values. This requires a consistent strategy for the detection of outliers in terms of very rare events. The actual strategy used in the European snow load research is less appropriate, since too many events are not detected and a large number of events are erroneously classified as outlier. Aim of the project is the development and application of an improved strategy, which especially considers unbiased estimators like BLUE. Thus, it becomes possible to analyse true outliers in a probabilistic consistent way. The accumulation and spatial distribution of snow on roofs greatly depends on the wind speed. The snow-wind climate of Germany can be sub-divided into three basic types. Type I shows for large snow loads virtually deterministic wind speed values. Then, the shape parameters can be specified on the load model which has been developed in the first period of the project. Type II features scattering wind speeds, which requires extensions of the basic convolution integrals. Only for type III storm and snow occur simultaneously. Then, consistent combination rules are required for these two climatologic actions.

气候作用编纂的基本任务之一是根据单站观测确定全区域设计值。估计值的统计稳定性很大程度上取决于集合的大小。对于每个单站的估计以及地统计插值来说都是如此，即对单站集合采样的观测值越多，并且使用越多的站作为地统计插值的输入，结果的统计稳定性就越高。对于德国的224个站点，可以直接根据观测到的水当量进行极值统计，这些水当量平均为37年。开发的概率等效雪密度模型与使用独立事件而不是年度极端事件的新方法相结合，导致了相当大的集合规模，平均有 130 个条目。将单站模型转换为区域模型可以分析另外 525 个站，这些站仅提供积雪高度的观测结果。进一步的改进，即减少统计不确定性，是通过引入超级站来实现的，这些超级站按照一致的概率策略结合单个站的观测结果。然后，可以以足够的统计稳定性来识别分布类型。该项目的目的是在雪荷载极值统计范围内利用观测到的雪高数据和相应设计值的统计最佳规范。这需要采用一致的策略来检测非常罕见事件的异常值。欧洲雪荷研究中使用的实际策略不太合适，因为没有检测到太多事件，并且大量事件被错误地归类为异常值。该项目的目标是开发和应用改进的策略，特别考虑像 BLUE 这样的无偏​​估计量。因此，可以以概率一致的方式分析真实的异常值。屋顶积雪的积累和空间分布很大程度上取决于风速。德国的雪风气候可分为三种基本类型。 I 型显示大雪荷载几乎确定的风速值。然后，可以在项目第一阶段开发的荷载模型上指定形状参数。 II型的特点是散射风速，需要对基本卷积积分进行扩展。仅适用于Ⅲ型风暴和降雪同时发生的情况。那么，这两种气候作用需要一致的组合规则。